Video quality measurements and analysis may require each frame in a test video sequence to be played at the same time as the corresponding frame of a reference video sequence is played. This may be referred to as temporal registration of the test video sequence and the reference video sequence.
Temporal registration may be difficult to perform, either manually or by an automated method, due to differing video formats, differing frame rates, temporal distortions, temporal impairments and other differences between the test video sequence and the reference video sequence. In addition, encoding, transporting, broadcasting, distributing, decoding, and other processing of video, may contribute to one, or more, frames being skipped in a video sequence as illustrated in the exemplary reference and test sequences:
Reference Sequence:A B C D E F G Test Sequence:A B C D E G H,where like-letters denote corresponding video frames, also considered frames, between the reference sequence and the test sequence. In this example, frames A, B, C, D and E are aligned. However, because of reference-video-sequence frame F being skipped in the test video sequence, the last two frames are mismatched between the test video sequence and the reference video sequence.
Automated methods and systems to measure the number and location of skipped frames in a test video sequence relative to a reference video sequence may be desirable. In particular, it may be desirable to have measurement methods and systems that are robust in the presence of digital compression artifacts, random noise, quantization error, and other non-linear and linear distortions and interferences. Additionally, it may be desirable to have measurement methods and systems that do not require a priori knowledge of the video content, aspect ratio, DUT (Device Under Test) pixel clock, frame rates, video parameters, including relative spatial mapping, for example, horizontal scaling, vertical scaling, offset and cropping, and other video factors. Accurate and computationally efficient methods and systems may also be desirable.